The present invention relates to a sensor arrangement and a method of acquiring the surface layer properties of a metallic target, it being presumed that the conductivity and the permeability of the base metal of the target are known.
The acquisition of the surface layer properties of a metallic target is understood to include, for example, the examination of the homogeneity of the surface layer of the target, or also the detection of damage in the structure of the target surface. Special importance is attached to the application of the present invention in measuring coating thicknesses. In this instance, the target consists of a metallic base material and a coating or plating, which corresponds to the surface layer, and is preferably formed by a metallic material other than the base material. Thus, the base material serves as a carrier for the coating or surface layer. In practice, it is often necessary to determine the thickness of such a coating. However, this will turn out to be problematic, when the coating is not to be damaged during this process.
While methods of measuring the thickness are known for foils, strips, or the like of nonconductive materials, they are however not easily transferable to the measuring of the coating thickness of a metallic surface layer on a metallic base material either with respect to the sensors in use, or with respect to the method or the measuring principle underlying the method. This all the more, inasmuch as the method of measuring employed for a certain measuring application and in particular the types of sensors employed within the scope of this method are primarily selected in dependence on whether the layer, whose thickness is to be determined, consists of a conductive or a nonconductive material.
It is therefore the object of the present invention to provide a sensor arrangement and a method of acquiring surface layer properties of a metallic target, which permit a measurement to be performed that is nondestructive and as noncritical as possible with respect to the exactness of the sensor positioning.